Safety mechanism for elevators



Jan. 15, 1935. J, SPRA'GUE SAFETY MECHANISM FOR ELEVATORS Filed Oct. 10,1928 ATTRNEY INVENTOR Patented Jan. 15, 1935 UNITED STATES SAFETYMECHANISM FOR ELEVATORS Frank J. Sprague, New York, N. Y., assignor toWestinghouse Electric & Manufacturing Company, a corporation ofPennsylvania Application October 10, 1928, Serial No. 311,510

16 Claims.

My invention relates to safety devices for elevators and moreparticularly to means for actuating such safety devices.

In order to provide for the safe operation of elevators, each car isusually supplied with a safety or car-stopping device comprising twopairs of gripping jaws that are disposed underneath the car in positionto engage the guide rails at the sides of the car when the car falls andbring itto a stop. In some cases, the gripping jaws are applied to theguide rails by means of stored-up power, such as may be obtained fromcompressed springs in conjunction with operating wedges. In other cases,the gripping jaws are applied to the guide rails by means of wedgeshapedexpanding members that are projected by screw action of a safety cabledrum. In either case, the release of the stored-up power or theoperation of the rotatable cylinder is usually eifected by a safety ropewhich is firmly secured to a governor rope. The governor rope isreleasably attached to the car, from which it runs to an overhead sheavemounted in the upper part of the hatchway, and thence to and around a'counterweighting sheave and back to the car. Normally, the governor ropemoves with the car and rotates the overhead sheave. Attached to theoverhead sheave is a centrifugal governor which, when rotated above apredetermined speed, releases a locking device that firmly grips thegovernor rope and arrests its movement, if the car is descending. Whenthe movement of the governor rope is arrested, it is automaticallyreleased from the car by the releasable attachment; thereupon, thecontinued downward movement of the car causes the governor rope to pullon the safety rope and thereby release the stored-up power or operatethe rotatable cable drum to apply the gripping jaws to the guide railswith increasing pressure, until the car is brought to a stop.

Inasmuch as the operation of the safety jaws is initiated and controlledby a centrifugal governor set to operate at some maximum speed above theusual speed at which the car runs, it may properly be called aspeed-controlled system. Such speed-controlled systems have been in usefor many years, but, since their introduction, the normal running speedsof many elevator cars have been materially increased, largely because ofthe increased height of buildings and also because of the necessity forincreasing the work performed by the individual elevators. When thespeed .of a car is increased it follows that the maximum speed at whichthe centrifugal governor will become effective to stop the car must alsobe increased accordingly.

Modern elevators are being operated at normal high speeds ranging from600 to 800 feet per minute, and even 1000 feet per minute and over isproposed.

It is inherent in a speed-controlled systemlthat the speed attained bythe car before the speedresponsive device will trip must be in excess ofthe normal speed by a considerable margin, usually about 25%. In otherwords, the elevator must attain speeds of from 750 to 1250 feet or moreper minute before eveninitiating the action, of the safety system.Since, also, in most safety systems, an additional time elapses beforethe jaws actually grip the rails, it is obvious that the mass of anelevator car moving at such high rates of speed will require anexcessive braking force to bring it to rest within a reasonabledistance, this force varying as the square of the attained speed for anypredetermined distance and load.

With the usual safety grips now used, the brakingforce must be appliedto the guide rails, and, in most cases, such application will distortor. cut them to such an extent that, after a single application of thesafety grips, repairs are necessary. Moreover, should the car get out ofcontrol either by-breakage of the cables or by'failure of some of theelectrical control apparatus, when the car is within a few floors of thelower limit. of travel, it may not attain such speed as will causetripping of the speed governor before the car reaches the bottom of thehatchway. In other words, the car may approach the lower limit of travelat a speed somewhat under or over its normal maximum speed, and, in thecase of a car operating normally at 800 or more feet per minute, it willbe extremely difiicult to stop it with oil buffers or other safetystopping devices which the-car will strike at the bottom of the hatchwaywithout serious injury to such buffers or to the car and its occupants.

In addition to failure of cables, a more frequent occurrence is to havethe car get out .of

control of the attendant by failure of some of the motor, brake orelectrical control apparatus, and, in this case, the car may descendthrough a relatively great distance in spite of the attempts of theattendant to stop it, but the speed of the car, in such case, may neverrise to such value as to trip the safety governor. If a runaway carreaches the lower limit of travel before the speed becomes great enoughto trip the governor the car will be broughtlto an abrupt and violentstop at the bottom of the hatchway. These facts all have additionalimportance if two elevators, one over another, are operated in a singlehatchway.

Furthermore, while it is the usual practice to inspect the safetyappliances on elevator cars frequently, such inspection seldom consistsof any actual test of the operative condition of the safety devices,particularly, the actual setting of the safety jaws, since thedifficulties encountered in operating the car at such high speed as willcause the governor to trip are considerable as is also the consequentprobability of damage to the guide rails when the safety jaws areactually applied, with the car operating at the necessary speed. Hence,the inspection usually consists in determining that the governor cableis in good condition, that the tripping device is free to operate andthat the safety jaws appear, upon visual inspection, to be in operativecondition. Therefore, in the interest of general security, the safetyapparatus should be such that all the parts on which the safety of thecar depends may be readily tested by actual application under differentconditions of speed and'rates of acceleration.

In seeking to provide mechanism for operating elevator safety devicesthat does not embody the inherent objectionable characteristics of thespeed-control mechanism, I have discovered that such a predeterminedrate of acceleration as will follow when a car starts to fall or startsto run away in a downward direction may be employed to initiate theoperation of the safety device to stop the car.

This will be understood when it is considered that, while the rate ofacceleration, by reason of gravity, in free falling, is approximately 32feet per second per second, the rate of acceleration of any car duringits normal operation is rarely over one-third of the rate caused bygravity.

It is obvious that a change in the rate of acceleration occurs instantlywhen a car starts to fall or run away, and, therefore, that a rate ofacceleration may be selected which will be just as effective in thefirst one-fiftieth of a second after failure occurs to initiate thestopping of the car as it will be at the end of any period of timethereafter.

One of the objects of my invention is to provide for stopping a car assoon as it starts to fall or starts to run away in the downwarddirection.

Another object of my invention is to provide for stopping a falling carbefore it reaches a dangerous speed.

Another object of my invention is to provide for stopping a car beforeit reaches a high speed after it starts to run away.

A further object of my invention is to provide a safety mechanism for anelevator that shall be so quickly responsive to dangerous conditionsthat it will act to stop the car before it attains such high speed thatthe safety apparatus will be damaged in making a stop.

A further object of my invention is to provide a safety mechanism for anelevator which shall be operatively responsive to the rate ofacceleration-of the elevator and independent of the speed of theelevator.

A further object of my invention is to provide a safety mechanism forelevators that may be readily inspected and tested under variousconditions of actual operation.

A further object of my invention is to provide a safety mechanism forelevators that may be readily adjusted to approximate differentconditions so that it may easily be tested under a variety ofcircumstances.

A further object is to provide a means for initiating the action of thesafety device that may be easily and quickly reset by the attendant onthe car.

A further object is to provide a plurality of means for initiating theoperation of the safety device for the purpose of insuring its operationupon the occurrence of any dangerous condition.

A further object of my invention is to provide a safety mechanism forelevators that shall be responsive to a predetermined rate of downwardacceleration of the car, or an increase in the speed of the car to apredetermined maximum above its normal speed.

A further object of my invention is to provide a safety mechanism for anelevator that shall be responsive to a predetermined rate ofacceleration while the car is descending, but which will not be affectedby any change in the rate of acceleration or deceleration while the caris ascending.

A further object of my invention is to provide a safety mechanism for anelevator which may be responsive either to the speed of the elevator orto the rate of acceleration of the elevator, and which may be manuallyoperated at the will of an attendant on the elevator.

It is also an object of my invention to provide an elevator safetydevice that shall be simple and efficient in operation, and adapted forready and economical installation and maintenance.

Other objects of my invention will, in part, be obvious and will, inpart, appear hereinafter.

For an illustration of one of the many forms my invention may take,reference may be had to the accompanying drawing in which:

Figure l is a diagrammatic representation of an elevator embodying meansfor actuating its safety device constructed in accordance with myinvention;

Fig. 2 is a view, in side elevation, illustrating a modification of theelectroresponsive means for actuating the cable-locking device shown inFig. 1; and

Fig. 3 is a top plan view illustrating a modification of theacceleration-controlled device for initiating and effecting theoperation of the governor-rope-locking device shown in Fig. 1.

In Fig. 1 of the drawing, I have illustrated an elevator car Csupported, by a hoisting cable 11, between a pair of guide rails 12 and13. Secured to the bottom of the car C is the usual safety-grip device14 comprising two pairs of jaws l5 and 16 disposed to grip the guiderails 12 and 13 and stop the car when the car starts to fall or run awaydownwardly. A pair of operating screw rods 17 and 18 connect thegripping jaws 15 and 16, in the usual manner, to a safety-cable drum 19which, when rotated, causes the jaws to grip the guide rails. The meansfor rotating the safety-cable drum 19 comprises a safety rope 20, oneend of which is secured to, and wound around, the drum, and the otherend of which passes over a pair of sheaves 21 and 22 and is firmlyfastened to a governor rope 23, such as is usually provided on elevatorinstallations.

The governor rope 23 is releasably attached to the car by means of anysuitable yielding connection 24, and passes over a sheave 25 on acentrifugal governor 26, mounted at the top of the hatchway, for thepurpose of rotating the governor in accordance with the speed of the upand the down movements of the car.

further movement.

The governor 26 may be of any well known type and is illustrateddiagrammatically as having its sheave secured to a rotatable shaft 27 onwhich is mounted a gear wheel 28 that engages a cooperating gear wheel29 on an operating sleeve 30 keyed to the lift rod 36. Pivotally mountedon the upper end of the operating sleeve 30 is a pair of weightedgovernor balls 31 and 32 that are provided with lifting arms 33 and 34which are adapted to engage a collar 35 on the upper end of a rod 36 andraise it when the balls 31 and 32 are thrown outwardly, as the governorexceeds a predetermined maximum speed.

The rod 36 is journalled in the operating sleeve 30 and extendsdownwardly through a lever 38 that is fulcrumed in a standard 39 on thegovernor frame 40. Secured to the lower end of the rod 36 is a collar 41that engages the underside of the lever 38 and raises it when the rod israised by the action of the governor balls. A weight 42, attached to therod 36, determines the speed at which the governor balls will lift therod 36.

The right-hand end of the lever 38 extends under the cooperating end ofa pivotally mounted cam lever 43 in such manner that an upward movementof the lever 38 will raise the cam lever and force its gripping jaw 44to wedge the governor rope against a cooperating jaw 45 and lock therope against further movement. Thus, it will be seen that, if the car C,while descending, moves the governor rope to operate the centrifugalgovernor at a speed in excess of a predetermined maximum speed, thegovernor will actuate the jaw 44 and lock the governor rope against Whenthe governor rope is locked by the jaws 44 and 45, while the car isdescending, it will be pulled free from the yielding connection 24 andunwind the safety rope 20 from the safety-cable drum 19, therebyapplying the gripping jaws to the guide rails.

While the means thus far described for actuating the safety device onthe car is of a well known type which is responsive to the speed of thecar, I have also provided an additional means for actuating the safetydevice that is responsive to a predetermined rate of downwardacceleration of the car.

In the form of the invention illustrated in Fig. 1, the additional meanscomprises an electroresponsive device 47 for actuating the lever 38, arelay 48 for controlling the electroresponsive means, and anacceleration-controlled device 49 mounted on the car for controlling therelay.

The electroresponsive device 47 embodies a :weighted lever-actuatingmember 50 and an electromagnet 51. The weighted lever-actuating member50 is pivotally connected to the standard 39 by an arm 54 in such mannerthat it will be supported by the electromagnet 51 when the latter isenergized but will fall upon an extended portion 55 of the lever 38 whenthe magnet is deenergized and cause the lever to actuate the locking jaw44 in the same manner as when it is actuated by the centrifugalgovernor.

The electromagnet 51 is connected to a suitable source of powerrepresented by supply conductors L1 and L2 through the contact membersI) of the relay 48 in such manner that, when the relay is deenergized,the electromagnet 51 will be deenergized to drop the lever-actuatingmember 50.

The relay 48 for controlling the circuit for the electromagnet 51 of theelectroresponsive device 47 may be mounted at any suitable point, in thecar or in the upper part of the hatchway adjacent to the electromagnetand the centrifugal governor. When the relay isdeenergized, it may bereset by means of a push-button switch 56 that is mounted in the car ata point where it may be easily reached by the attendant.

The acceleration-controlled device 49 comprises a weighted member 60mounted on the'free end of an arm 61 which is pivotally attached to thecar or a casing in the car by a pin 62, and a pair of contact members 63and 64 associated with the weighted member and actuated thereby forcontrolling the circuit of the coil of the relay 48.

The contact member 63 is mounted on, and movable with, the weightedmember 60, while the contact member 64 is stationarily secured to thecar in such position as to engage the contact member 63 and support theweighted member in a horizontal position while the car is operatingnormally.

It will be seen, therefore, that, inasmuch as the weighted member 60merely rests upon the contact member 64 and is free to move upwardlytherefrom, if the rate of down acceleration or up deceleration of thecar is increased to a rate above approximately 32 feet per second persecond, it will cause the weighted member, by reason of its inertia, toseparate the contact member 63 from the contact member 64 and therebyopen the circuit for the relay 48.

In order that the weighted member 60 may be made effective to open thecontact members 63 and64 at any selected rate of acceleration betweenzero and 32 feet per second, it is partially supported by a tensionspring 65, the upper end of which is secured to a screw threaded member66 that is mounted in a bracket 67. A thumb nut 68 on the screw threadedmember 66 permits adjustment of the tension of the spring 65, and apointer 69, attached to the upper part of the screw threaded member,cooperates with a scale 70 to indicate the adjustment in terms ofacceleration rate. After the scale and pointer are properly calibrated,the device may be quickly set or reset to operate in response to anypredetermined rate of acceleration of the car.

The spring 65 may be adjusted to a point where it is entirely slack andat which the weighted member 60 will be entirely supported by thecontact member 64. With this adjustment, the spring has no materialvalue and it would require a downward acceleration or and upwarddeceleration exceeding 32 feet per second per second to cause anyrelative movement between the weighted member 60 and the car to open thecontact members 63 and 64.

If the tension of the spring 65 is increased until it takes one-half ofthe weight of the member 60, then acceleration at a rate exceeding 16feet per second per second will cause relative movement between theweighted member 60 and the car, thereby separating the contact members63 and 64. Also, if thespring is adjusted so that it takes, say,three-fourths of the weight of the member 60, the contact members 63 and64 will be separated when the rate of acceleration exceeds eight feetper second per second. In all cases, where the rate of accelerationexceeds the point for which the spring 65 is set, the contact members 63and 64 will be separated.

It should be noted that, by reason of the convenient manner in which thespring may be adjusted, the acceleration-controlled device 49 may be setto operate at very low rates of acceleration, and thereby permit testingof the safety apparatus by actual application thereof at such low speedsas will not damage the guide rails and the gripping jaws or placeexcessive strains on the car and the apparatus connected therewith.Furthermore, it facilitates the testing of the car at a variety ofspeeds and rates of acceleration and deceleration. By reason of having ascale and a pointer on the adjusting members, they may be reset readilyto their original positions after testing.

For the purpose of preventing the minor movements of the jolting of thecar, or vibration, from causing the weighted member 60 to separate thecontact members 63 and 64, the contact member 63 may be constructed ofspring material, to give a slight margin of movement before opening thecircuit, and its free end is disposed between a pair of lugs or stopmembers 71 and 72 on the weighted member. With this construction, if themember 60 moves only slightly with reference to the contact member 64,the contact member 63 will, by reason of its resilient characteristics,stay in contact with the contact member 64. However, if the movementaway from the contact member 64- is continued, the lug '72 will engagethe free end of the contact member 63 and carry it away from the contactmember 64.

In order to prevent the weighted member 60 from separating the contactmembers 63 and 64' any farther than is necessary to insure the openingof the relay circuit, a stop member 73 is provided at such point abovethe weighted memher as will limit its upward movement to the desiredextent. The limiting of the upward movement of the weighted member 60also makes it possible for that member to effect engagement of thecontact members 63 and 64 very quickly, and this, in conjunction with atime relay on the relay 48, prevents the setting of the safety device ona quick up-stop, as will be more fully explained later.

A normally closed push-button switch 74 is mounted in the car andconnected in the circuit of the relay 48, in order to enable theattendant to effect the operation of the safety device at any time hedesires by opening the switch and thereby deenergizing the relay.

As a further safeguard, the circuit for the relay 48 is also connectedthrough the normally closed contact members of a switch 75, which isconnected to the centrifugal governor 26 in such manner that it will beopened when the governor exceeds a predetermined maximum speed andthereby deenergize the relay.

The acceleration-controlled device 49 is not limited in action to downacceleration but may respond to nip-deceleration on sudden stopping, butthe difference between down-acceleration and Lip-deceleration isimportant in that the former is of a continuing character and tends tohold the contact members 63 and 64 separated, while deceleration on asudden up-stop is momentary and immediately drops to zero. Withcontinued down-acceleration, the weighted member 60 will separate thecontact members 63 and 64 and keep them separated, whereas, on excessiveup-deceleration in stopping, the contact members 63 and 64 will beseparated and re-engaged very quickly, that is, in a small fraction of asecond, by reason of the fact that the upward travel of the weightedmember is limited by the stop member 73.

Therefore, in order to have the mechanism differentiate betweendown-acceleration and updeceleration, a discharge resistance '79 isshunted across the terminals of the relay 48 to slightly delay itsaction. This delay, although operating equally for either direction,will not interfere in any practical manner with the operation of thesafety device on the down-movement of the car but will prevent theoperation of the safety device on a too sudden up-stop because thelatter influence is of very short duration.

Assuming, for example, that the shunt resistance 79 on the relay 48delays its action for one twenty-fifth of a second and that the travelof the weighted member 60 is so limited by the stop member '73 that, onan excessive up-stop deceleration, the contact members 63 and 64 will beseparated and re-engaged within that time. Obviously, under theseconditions the relay 48 will not open. On the other hand, adown-acceleration rate above the predetermined rate for a periodexceeding one twenty-fifth of a second will cause the contact members 63and 64 to be separated and to remain separated for a sufficient lengthof time to deenergize the relay 48. Inasmuch as the free fall of a bodyunder the influence of gravity for the first one twentyfifth of a secondamounts to only a fraction of an inch, and the speed of the body isstill low, a little over one foot per second, a delay of onetwenty-fifth of a second in initiating the operation of the safetydevice when the car starts to fall is of no moment.

The invention may be best understood by an assumed operation of theapparatus shown in Fig. 1.

Assuming that the car C is at rest at the top of the hatchway and thatthe push button of switch 56 has been pressed to energize the relay 48and the electromagnet 51 for operation, the closing of the push-buttonswitch 56 completes a circuit for energizing the relay 48 that extendsfrom supply conductor L1, through conductor 81, the coil of relay 48,conductor 82, the contact members of push-button switch 56 and conductor83, to supply conductor L2. When the relay 48 is energized, it closesits contact members a and completes a holding circuit for itselfindependent of the button 56 that extends from supply conductor Ll,through conductor 81, the coil of relay 48 conductors 82 and 85, thecontact members a of relay 48, conductor 86, the contact members ofswitch 75, conductor 88, the normally engaged contact members 63 and 64of the acceleration-controlled device 49, conductor 89, the normallyclosed contact members of push-button switch 74 and conductor 91, tosupply conductor L2.

The closing of the contact members I) on the relay 48 completes acircuit for energizing the electromagnet 51 that extends from supplyconductor L1, through conductor 92, the contact members I) of relay 48,conductor 93, the coil of electromagnet 51 and conductor 94, to supplyconductor L2. The electromagnet 51 being energized, the lever-actuatingmember is lifted and suspended above the left-hand end of the lever.

Assuming now that the spring 65 has been adjusted, by the operation ofthe thumb nut 68, to such point that the acceleration-controlled device49 will become effective to deenergize the relay 48 when the rate ofdown-acceleration of the car exceeds sixteen feet per second per second,and that the car has started down the shaft and, for any reasonwhatever, gotten beyond control of the operator and has started to fall;then, as soon as the rate of acceleration exceeds the pre- "member 102.

determined "rate of sixteenfeet per second per second at which theacceleration-control device has been set to operate, the weighted member60 will separate contact members 63 and 64 to open the circuit whichenergizes the coil of the relay 48, thereby deenergizing the relay andcausing it to separate its contact members I). The separation of thecontact members I) of the relay 48 opens' the circuit for theelectromagnet 51 and deenergizes it, thereby causing the weightedlever-actuating member 50 to drop on the extended portion 55 of thelever 38 and actuate the lever. The actuation of the lever 38 operatesthe locking jaws 44 and 45 and locks the governor rope 23 againstfurther movement, thereby causing the car, as it falls, to pull thesafety rope 21 from the cylinder 19 and thus apply the gripping jaws 15and 16 to the guide rails 12 and 13 to stop the car.

Although I have described the operating force as exerted by a weightedmember, it is to be understood that this term is not used in a limitedor specific sense, and that any equivalent mechanism representingstored-up energy, held in a state of equilibrium, may be used on, forexa l-- ple, a spring or the combination of a weight and a-spring.

When the car is again ready for operation, after being stopped and thesafety device and the governor-rope locking jaws 44 and 45 have beenreset in a well-known manner, the relay 48 may be reenergized to causethe'electromagnet 51 to pick up the lever-actuating member 50 and againplace the safety mechanism in condition for operation, by the attendantpressing the push-button of switch 56 to close the circuit for therelay; or, if desired, the actuating member may be set in place manuallyand then held there by the energized magnet.

In the modified form of the electroresponsive device illustrated in Fig.2, a weighted lever-actuating member 95, similar to Weight 50 (Fig; 1),is pivotally attached, by means of arm 96, to the standard 39 in suchposition that it will, when dropped, hit the extended portion 55 of thelever 38 and actuate the lever. Mounted on the top of thelever-actuating member is a catch 9'7 adapted to receive a latchingmember 98 that is controlled by an electromagnet51 which is also mountedon the upper part of the standard 39.

A tension spring 99 is provided for so biasing the latching armature 98away from the catch 9'7 that, when the electromagnet 51 is deenergizedby the opening of the relay 48, the lever-actuating member 95 will bereleased to fall upon the extended portion 55 of the lever 38.

In resetting this modified device, it is necessary to raise the weightedmember 95 after the electromagnet 51 is energized until the catch 97 isengaged by the latching armature 98.

The modified form of the acceleration-controlled device 49, illustratedin Fig. 3, comprises a disk 100 that may be secured to a rotating mem--ber of the usual speed-controlled means for op-- erating the safetydevice, such as the governor shaft 27 upon which the sheave 25 ismounted. The disk is secured to the shaft so that it'will rotatetherewith. Rotatably mounted upon the hub 101 of the disk 100 is aweighted member 102 corresponding, in function, to the weighted member60 shown in Fig. 1. Acontact member 103 is mounted upon andinsulatedfrom the disk 100 for the purpose of engaging a contact spring member104 that is mounted on the weighted These contact members correspond,

in function, to the contact members 63 and 64.

A tension spring 105 is mounted upon the disk 100 and connected to'theend of the'weighted member 102 opposite to that on which contact member104 is mounted for the purpose of biasing the weighted member to aposition where the contact members 103 and 104 will be closed. Thespring 105 is secured to the disk 100 by means of a screw-threadedmember 106 that may be'adjusted by a thumb nut 107 in a manner similarto the device illustrated in Fig. 1. The contact member 104 on theweighted member 102 may be connected in the circuit of the relay 48 bymeans of an annular contact ring 108 and a contact brush 109, while thecontact member 103 on the disk 100 may be connected in the circuitby'means of a contact ring 110 and a cooperating contact brush 111. Astop member 112 is attached to the disk 100 for the purpose oflimitingthe movement of the weighted member 102.

In this form of the device/the spring 105-'cooperates with the disc 100to cause movement of the weighted member 102. If the disc 100 isaccelerated at a certain rate, due to some external force, the spring105 must exert a sufiicient force on the member 102 to causeit to assumethe same rate of acceleration. If, now, the force required to acceleratethemember 102 at this "rate is in excess of the strength of the spring,the member 102 will move at a lower rate than the disc, and the contactmembers 103*and 104 will be separated.

As the contact members 103 and 104are separated, of course, the spring105is' elongated, and, therefore, exerts a greater force. The contactmembers 103 and 104 will, therefore, be separated to such an extent thatthe force exerted by spring 105 is just equal to the force required toaccelerate the member 102 at the certain rate. This rate may be varied,as described, by means of the adjusting screw 107.

It will thus be seen that, in this modified form of theacceleration-controlled device, the weighted member 102 will rotate withthe disk 100 until such time as the rate of acceleration exceeds thepredetermined'maximum for whi'chthe device has been set. 'Whenthispredetermined point is reached and passed, the inertia of 'the weightedmember 102 will cause the contactmemhere 103 and 104 to separate andthereby open the circuit for the relay '48 to deenergize theelectroresponsive device 47 and effect an application of the safetydevice 14 onthe car.

It will be seen, therefore, that I have provided a safety mechanism forelevator cars that will operate upon the first occurrence of dangerousconditions, that may be operated 'by the car attendant at any time, thatmay be tested under many difierent conditions, and that has embodied init a plurality of means for ensuring the operation of the safety deviceso that, if one fails to function another will be brought into action toeffect the stopping of the car.

I claim as my invention:-

1. A safety mechanism for an elevator car comprising a safety device andmeans responsive to only continued acceleration of the car at apredetermined rate for causing the operation of the safety device tostop the car.

2. A safety mechanism for an elevator car comprising a safety device andmeans responsive to only a continued down a'cceleration'of the car at arate above a predetermined value for causing car.

3. A safety mechanism for an elevator car comprising a safety device,means for effecting the operation of the safety device to stop the car,a member having stored up potential energy for operating the means foreffecting operation of the safety device, an electromagnet, means forenergizing the electromagnet to maintain the member having stored uppotential energy in an ineffective position and means responsive to apredetermined rate of down acceleration of the car for deenergizing theelectromagnet.

4. A safety mechanism for an elevator car comprising a safety device,means for effecting the operation of the safety device to stop the car,a weighted member for operating the means for effecting operation of thesafety device, an electromagnet, means for energizing the electromagnetto maintain the weighted member in an ineffective position and meansresponsive to a predetermined rate of down acceleration of the car fordeenergizing the electromagnet.

5. A safety mechanism for an elevator car comprising a safety device,means for operating the safety device to stop the car, means responsiveto a predetermined rate of acceleration of the car for actuating saidsafety operating means and means for retarding the action of the safetyoperating means for a predetermined length of time.

6. In a safety mechanism for an elevator car, the combination with asafety device, a governor rope, means for locking the governor rope toeffeet the operation of the safety device, a centrifugal governoroperated by the governor rope for actuating the locking means when thespeed of the car exceeds a predetermined maximum speed, and anadditional means for actuating the locking means comprising a weightedactuating member, an electromagnet for controlling the weightedactuating member, a circuit for the electromagnet, and means operablyresponsive to a predetermined rate of down acceleration of the car forcontrolling the circuit of the electromagnet.

7. A safety mechanism for an elevator car comprising a safety device forstopping the car, an electro-responsive device for effecting operationof the safety device, a circuit for controlling the electroresponsivedevice, and means operably responsive to a predetermined rate of downacceleration of the car for controlling said circuit, saidacceleration-controlled means comprising a movable weighted member and apair of relatively movable contact members disposed to be actuated bymovements of said weighted member, and means for preventing effectiveactuation of said contact members by minor movements of the weightedmember.

8. A safety mechanism for an elevator car comprising a safety device forstopping the car, an electroresponsive device for effecting operation ofthe safety device, a circuit for controlling the electroresponsivedevice, and means operably responsive to a predetermined rate of downacceleration of the car for controlling said circuit, saidacceleration-controlled means comprising a movable weighted member, apair of relatively movable contact members disposed to be actuated bymovements of said weighted member, one of said contact members beingconstructed of resilient material to thereby prevent effective actuationof said contact members by minor movements of said weighted member.

9. In a safety mechanism for elevators, a safety device and meansoperably responsive to a predetermined rate of acceleration foractuating said safety device, said acceleration-responsive meanscomprising a support movable in accordance with movements of saidelevator, a member of relatively large mass mounted on said support formovement relative thereto, means for biasing said member to aid movementthereof in a direction corresponding to one direction of elevatormovement and to oppose movement in the opposite direction and means foractuating said safety device controlled by relative movement of saidmember and said support.

10. In a safety mechanism for elevators, a safety device and meansoperably responsive to a predetermined rate of acceleration foractuating said safety device, said acceleration-responsive meanscomprising a support movable in accordance with movements of saidelevator, a member having relatively large mass mounted on said supportfor movement relative thereto, means for biasing said member to aidmovement thereof in a direction corresponding to one direction ofelevator movement and to oppose movement in the opposite direction,means for actuating said safety device controlled by relative movementof said member and said support, and means for varying the force of saidbiasing means.

11. In a safety mechanism for elevators, a safety device and meansoperably responsive to a predetermined rate of acceleration foractuating said safety device, said acceleration-responsive meanscomprising a support movable in accordance with movements of saidelevator, a member having relatively large mass mounted on said supportfor movement relative thereto, means for biasing said member to aidmovement thereof in a direction corresponding to one direction ofelevator movement and to oppose movement in the opposite direction,means for actuating said safety device controlled by relative movementof said member and said support, means for varying the force of saidbiasing means, and calibrating means for indicating the force of saidbiasing means.

12. In a safety mechanism for an elevator car, the combination with asafety device comprising means normally movable in accordance with themovement of the car and means operably responsive to relative movementof said movable means and said car for stopping the car, of means foreffecting relative movement of said movable means and the car to causesaid stopping means to stop the car, including a weighted memberadapted, when unsupported, to effect a restraint upon said movable meansand thereby cause relative movement thereof with respect to the car, anelectro-responsive means adapted, when actuated, to magnetically supportsaid weighted member and to render it ineffective to cause relativemovement of the movable means and the car, and means operably responsiveto a predetermined rate of acceleration of said car for causing saidelectro-responsive means to be ineffective to support said weightedmember.

13. In a safety mechanism for an elevator car, the combination with asafety device comprising means normally movable in accordance with themovement of the car and means operably responsive to relative movementof said movable means and the car, for stopping the car, of means foreffecting relative movement of said movable means and the car to causesaid stopping means to stop the car, including a weighted memberadapted, when unsupported, to effect a restraint upon said movable meansand thereby cause relative movement thereof with respect to said ear,eleetro-responsive means adapted, when actuated, to efiect a support forsaid weighted member and prevent it from causing relative movement ofsaid movable means and the car, and means for controlling saidelectro-responsive means including a circuit for connecting saideleetro-responsive means to a source of energy, relay means aetuable tocomplete said circuit and effect the actuation of saidelectro-responsive means, and means operably unresponsive to aceeleration and deceleration of the car below a predetermined rate formaintaining said relay means actuated and operably responsive toaceeleration and deceleration of the car above said predetermined ratefor effecting the de-actuation of said relay means.

14. In a safety mechanism for an elevator car, a safety device operabletostop a car, means including electro-responsive means actuable toprevent operation of said safety device, means including means operablyresponsive to acceleration and deceleration of the car above apredetermined rate, for causing said electro-responsive means to beineffective to prevent operation of said safety device, and means forretarding the operation of said safety device for a predetermined time.

15. In a safety mechanism for an elevator car, the combination with asafety device comprising means normally movable in accordance with themovement of the car and means operably responsive to relative movementof said movable means and the ear for stopping the ear, of means foreffecting relative movement of said movable means and the ear to causesaid stopping means to stop the car, including a Weighted memberadapted, when unsupported, to effect a restraint upon said movable meansand thereby cause relative movement thereof with respect to the car,electro-responsive means adapted, when actuated, to effect a support forsaid weighted member and thereby prevent it from causing relativemovement of said movable means and the car, and means for controllingsaid eleetro-responsive means to cause it to effect no support for saidweighted member, including means operably responsive to acceleration anddeceleration of the car above a predetermined rate for deaetuating saidelectro-responsive means, and means for retarding the de-actuation ofsaid eleetro-responsive means a predetermined time after the operationof said acceleration and deceleration responsive means.

16. In a safety mechanism for an elevator ear, the combination with asafety device comprising means normally movable in accordance with themovement of the car and means operably responsive to relative movementof said movable means and the car, for stopping the car, of means foreffecting relative movement of said movable means and the car to causesaid stopping means to stop the car, including a weighted memberadapted, when unsupported, to effect a restraint upon said movable meansand thereby cause relative movement thereof with respect to said car,eleetro-responsive means adapted, when actuated, to effect a support forsaid weighted member and prevent it from causing relative movement ofsaid movable means and the car, and means for controlling saidelectro-responsive means including a circuit for connecting saidelectro-responsive means to a source of energy, relay means aetuable tocomplete said circuit and effect the actuation of saidelectro-responsive means, means operably unresponsive to accelerationand deceleration of the car below a predetermined rate for maintainingsaid relay means actuated and operably responsive to acceleration anddeceleration of the ear above said predetermined rate for eifeeting thede-aetuation of said relay means, and means for retarding thede-aetuation of said relay means a predetermined time after the saidacceleration and deceleration responsive means operates to effect itsde-actuation.

FRANK J. SPRAGUE.

